The emails came six months after Menendez raised concerns about the Dominican government’s port security in a Senate hearing with senior officials from the State and Commerce departments. A company run by Dr. Salomon Melgen, Menendez’s biggest political donor, has pushed to secure a lucrative port security contract with the Dominican government.

In the emails, an unidentified staffer for Menendez told U.S. Customs and Border Protection that the Dominican government wouldn’t use any U.S.-supplied security equipment as effectively as the port’s private contractor, which the aide did not mention by name. “My boss’ concern is that the CBP equipment will be used for ulterior purpose and asks that you hold off on the delivery of any such equipment until you can discuss this matter with us,” the staffer wrote.

The Associated Press reviewed the content of the emails, which were first disclosed Monday by The New York Times.

A spokeswoman for Menendez’s office, Tricia Enright, told AP on Monday that “our office was merely inquiring about and asking for a briefing on something that it turned out wasn’t even happening.” Enright said Menendez’s office did not contact the agency to halt any equipment transfer. “A transfer was never planned in the first place, so any suggestion we stopped it makes little sense.”

Separately, Menendez acknowledged last week that his office had contacted U.S. health agencies in a way that would help Melgen, whose private jet Menendez used for two personal trips to the Dominican Republic. Menendez said he contacted the U.S. Centers for Medicare & Medicaid Services to ask about billing practices and policies. The contacts came during a dispute between CMS and Melgen. The FBI recently searched Melgen’s offices.

Menendez has also acknowledged that he flew on Melgen’s private plane and failed, initially, to properly pay for the trips. He told reporters he reimbursed some $58,500 from his personal funds. The Senate Ethics Committee is investigating.

In the January emails, the Menendez aide asked Customs whether the U.S. planned to donate cargo-screening equipment to the Dominican government. The aide wrote that “individuals who do not want to increase security in the DR (Dominican Republic) might be holding up the fulfillment of a port security contract.” The staffer added that “these elements (possibly criminal) want CBP to give the equipment because they believe the government use of the equipment will be less effective than the outside contractor.”

A CBP official replied that there were no plans to donate any screening equipment, adding that “the CPB has not agreed to any expanded operations in the Dominican Republic and hasn’t provided any additional equipment.”

The “outside contractor” currently selected to provide cargo screening in the Dominican Republic is ICSSI, a Dominican company that was partially bought in 2011 by Boarder Support Services, a company based in West Palm Beach, Fla. Corporation records held by the Florida Department of State show Melgen as Boarder’s owner.

Last July, at a Senate Foreign Relations Committee hearing, Menendez pressed two senior U.S. officials about problems between the Dominican government and the unnamed port screening contract. Menendez suggested the government’s port security was endangered by its reluctance to deal with the unidentified company.

The ICSSI firm now partially owned by Melgen signed a contract in 2002 to provide screening throughout the country but the government suspended the deal in 2004 before it went into effect, claiming the contract was too expensive and the bidding was not competitive. Melgen’s company has been trying to reinstate the contract, which is tied up in Dominican courts. The Times has reported the contract could be worth as much as $500 million over 20 years.

The events have engulfed Menendez, 59, just as he assumed the chairmanship of the Senate Foreign Relations Committee, succeeding former Sen. John Kerry, D-Mass., who resigned to become secretary of state.

Melgen has been a friend and political supporter of Menendez’s for many years. Last year, Melgen’s practice gave $700,000 to Majority PAC, a super political action committee set up to fund Democratic candidates for Senate. Aided by Melgen’s donation, the super PAC became the largest outside political committee contributing to Menendez’s re-election, spending more than $582,000 on the senator’s behalf.